1. Technical Field
The present invention relates to a junction box for power sources, and specifically to a junction box for electrically connecting to a photovoltaic panel.
2. Description of Related Art
A photovoltaic module or photovoltaic panel is a packaged interconnected assembly of photovoltaic cells, also known as solar cells. Since a single photovoltaic module can only produce a limited amount of power, commercial installations include several modules or panels interconnected in serial and in parallel into a photovoltaic array. Electrical connections are made in series to achieve a desired output voltage and/or in parallel to provide a desired amount of current source capability. A photovoltaic installation typically includes the array of photovoltaic modules, an inverter, batteries and interconnection wiring.
When part of a photovoltaic module is shaded, the shaded cells do not produce as much current as the unshaded cells. Since photovoltaic cells are connected in series, the same amount of current must flow through every serially connected cell. The unshaded cells force the shaded cells to pass more current. The only way the shaded cells can operate at a higher current is to operate in a region of negative voltage that is to cause a net voltage loss to the system. The current times this negative voltage gives the negative power produced by the shaded cells. The shaded cells dissipate power as heat and cause “hot spots”. Bypass diodes are therefore integrated with the photovoltaic modules to avoid overheating of cells in case of partial shading of the photovoltaic module.
Blocking diodes may be placed in series with cells or modules to block reverse leakage current backwards through the modules such as to block reverse flow of current from a battery through the module at night or to block reverse flow down damaged modules from parallel-connected modules during the day.
Electronic modules may be integrated with the photovoltaic modules which perform electrical conversion, e.g. direct current (DC) to direct current conversion, electrical inversion, e.g. micro-inverter, or other functions such as monitoring of performance and/or protection against theft.
U.S. Pat. No. 7,291,036 discloses a photovoltaic connection system including a connection box with for surface mounted diodes mounted on a printed circuit board inside of the connection box.
The connection box optionally includes a metal plate mounted inside the lid of the connection box as a heat sink for dissipating heat from the diodes.
The term “cable gland” as used herein refers to a device used for the entry of electrical cables or cords into electrical equipment and is used to firmly secure an electrical cable entering a piece of electrical equipment.
The term “in situ” in the context of the present invention refers to bonding or attaching during manufacture, e.g. injection molding, of a part as opposed to attaching after manufacture of the part.